The present invention relates to multi-layer thermoplastic composites.
Polyamides (hereinafter abbreviated to PA) generally have good mechanical properties, in particular high strength, but also exhibit a poor barrier effect; thus polar substances can easily migrate through polyamides. This constitutes a major problem for fuel lines, for example, in which alcohol-containing felt is transported.
Ketone resins are formed from alkaline-catysed self condensation of ketones cyclohexanone, methylcyclohexanone), or from co-condensation of ketones (acetone, butanone, acetophenone, cyclohexanone, methylcyclohexanone) with formaldehyde-producing, nonsaponifiable and neutral reacting resins (synthetic resins) of light colour and softening ranges of 80-130 C. Co-condensates of ketones (e.g., cyclohexanone) with long chain aldehydes are of no technical significance. The ketones can be divided into acetone, acetophenone resins, etc., depending ion the starting ketone. Ketones from mixtures of different ketones are also known.
Polyketone polymers (hereinafter abbreviated to PK) are known in the art. As an example, United States patent U.S. Pat. No. 4,880,903 describes linear alternating polyketone terpolymers based on carbon monoxide, ethylene and other olefmically unsaturated hydrocarbons such as propylene.
U.S. Pat. No. 4,843,144 describes a process for the production of linear alternating polyketone-polymers from carbon monoxide and at least one ethylenically unsaturated hydrocarbon, employing palladium catalysts.
Other aliphatic polyketones based on ethylene, carbon monoxide and propylene have been described, for example in European patents EP-A-0,457,374 and EP-A-0,569,101, and are sold under a variety of trade names.
U.S. Pat. No. 5,232,786 describes multi-layer structures containing aliphatic polyketones and polyamides. The individual layers are, however, only mechanically bonded and characterized in that the individual layers can easily be separated by hand. In practice, in particular when used in car manufacturing in which hoses and pipes are constantly in contact with fuiels, a permanent bond which cannot be separated by external influences is required. U.S. Pat. No. 5,232,786 describes a terpolymer based on PA6, PA66 and PA12, which inseparably bonds to the polyketone. Copolymers, however, have the disadvantage of having low melting points, low crystallinity and poor crystallisability, which results in reduced resistance to gasoline and slow processing.
EP-A-0,569,101 describes multi-layer systems of polyketone polymers (PK) and polyamides (PA) which contain polymerised-in units of hexamethylenediamine and adipic acid. However, the layers in pipes manufactured from the two materials can be separated by hand. Such bond strengths are not suitable when making pipes and hoses specifically for transporting fuel. The swelling stress caused by contact with gasoline then leads to delamination of the layers.
Composite materials from polyamide and polyketone polymers with adhesively bonded layers are not so far known. The prior art only indicates the use of binding agents or compatibilising layers between layers of polyamides and polyketone which produce an adhesive bond. An adhesively bonded thermoplastic multi layer composite is vital for technical use, for example in automobile hoses.
The aim of the invention is thus to provide thermoplastic multi-layer composites in which for the first time, a polyamide layer is adhesively bonded to a polyketone layer.